Method for storing compressed air energy

Abstract

An economical compressed air energy storage (CAES) method effectively utilizing the capacity of space in the air storage portion in CAES plants to reduce the plant costs thereof is provided. An air storage portion is configured from a plurality of vessels, and a film to provide spaces with freely deformable shapes is disposed within each vessel. In the air compression step, the space on one side of the film within each vessel is filled in advance with a cushion gas, air is stored in the space on the other side of the film, and the cushion gas is changed into a fluid with a reduced volume to increase the amount of the air stored in the space on the other side of the film. In the air expansion step, fluid is heated and vaporized to decrease the amount of the air remaining on the other side of the film.

The invention claimed is: 
     
         1 . A method for storing compressed air energy comprising, a compression step of converting electricity into energy of compressed air and storing the compressed air in one or more vessels, and an expansion step of expanding the stored compressed air to recover the electricity, the compression step and the expansion step being performed alternately,
 wherein the vessels are such that, in all or part of the vessels, a single film or a plurality of films to form spaces having surfaces with freely deformable shapes is disposed within each vessel, thereby forming a plurality of partial spaces within the vessel,   by the start of the compression step, the partial space formed on one side of the surfaces of the film within the vessel is filled with a cushion gas,   in the compression step, the compressed air is stored in the partial space on the other side of the surfaces of the film within the vessel without being mixed with the cushion gas, and   the cushion gas is changed into a fluid with a reduced volume while retained within the vessel or sent to the outside of the vessel, thereby increasing the amount of the compressed air stored in the partial space on the other side of the surfaces, and   in the expansion step, the fluid present within or outside the vessel is vaporized and restored as the cushion gas in the partial space on the one side of the surfaces within the vessel, thereby decreasing the amount of the compressed air remaining within the vessel.   
     
     
         2 . The method for storing compressed air energy according to  claim 1 , wherein carbon dioxide alone or a mixture composed mainly of carbon dioxide is used as the cushion gas. 
     
     
         3 . The method for storing compressed air energy according to  claim 1 , wherein pressure ranges of the cushion gas are such that
 a minimum pressure in the expansion step is used within a range equal to or lower than a critical pressure of the cushion gas, and   a maximum pressure in the compression step is used at 90% or more of the critical pressure of the cushion gas.   
     
     
         4 . The method for storing compressed air energy according to  claim 1 ,
 wherein heat of compression generated by the compression of air is stored in the compression step, and   the stored heat of compression is utilized for at least one of heating the compressed air and heating the cushion gas in the expansion step.   
     
     
         5 . The method for storing compressed air energy according to  claim 4 ,
 wherein the method comprises a thermal storage step of storing the heat of compression, and   the thermal storage step at least includes a step of absorbing the heat of compression with water and storing the water which has absorbed the heat in a tank.